whois 172.18.0.1

 % This is the dn42 whois query service.

 % Information related to 'inetnum/0.0.0.0_0':
 inetnum:	0.0.0.0 - 255.255.255.255
 cidr:	0.0.0.0/0
 netname:	NET-BLK0-DN42
 policy:	reserved
 descr:	* The entire IPv4 address space
 mnt-by:	DN42-MNT
 status:	ALLOCATED
 source:	DN42